Loading ramps have been in common use since the days of the horse drawn farm wagon. For almost as long, the problem of positioning the ramps for storage and transport when not in use has perplexed users to the extent that numerous structures were developed to cope with the problem. Among them are a rear rack which drops to function as a loading ramp (U.S. Pat. No. 1,893,532), an end gate which is removable and usable as a loading ramp (U.S. Pat. No. 313,333), a loading ramp which hangs on the side of a side rack (U.S. Pat. Nos. 1,828,551 and 3,763,827) and a loading ramp which is positioned as a side board within the cargo space (U.S. Pat. No. 3,737,058). In most of the aforementioned structures, the ramp performs no function when in its stored position. In those structures in which the ramp functions as a tailgate when in transport position, a compromise must be made between a length which is insufficient (i.e., excessively steep) for loading heavy equipment on the one hand and, on the other hand, a rack which is of a height that creates clearance problems when in transit. U.S. Pat. No. 3,319,811 discloses a structure wherein a side barrier is mounted to a truck bed by an extensible and pivotal mounting at one end of the barrier so that it may be captively maneuvered so as to function as a loading ramp.
Also known in the prior art are structures which provide for extending the height of the side barriers of a load carrying bed. Such structures include gussets to support side boards (U.S. Pat. No. 1,587,552) and side extensions for pickup trucks (U.S. Pat. No. 2,856,225).
Turning to prior art relating to means for coupling a loading ramp with a load carrying bed or tailgate of a vehicle, U.S. Pat. No. 3,339,968 reveals a ramp which registers with coupling means for permanent attachment to the tailgate. The coupling means is bulky and requires a covering plate 50 to provide a smooth approach for movement of a load, and places the entire weight of a load on the tailgate and ramp coupling means. Convenient detachment after each use is not contemplated or provided for.